The invention concerns a circuit arrangement for telephone exchange systems, especially subscriber extension station installations, with additional data traffic, for example with teleprinters, whereby the teleprinters are connectable as data terminal equipment via data communication equipment and a switching device to the telephone exchange line of a subscriber station and whereby, for the production of teleprinter connections, besides the customary connection sets for the telephone traffic, by selection of a prescribed code number before selection of a subscriber number which characterizes the desired connection, selectable special connection sets are provided for the teleprinter traffic, which effect the switching from the telephone traffic to the teleprinter traffic at the individual subscriber stations. Arrangements of this sort are already known, for example, from the German A.S. No. 18,06,442. These known installations all function in the manner that first, a telephone connection is established to a desired subscriber within the same exchange installation or, via a trunk line to a subscriber of another exchange installation, and after completion of the desired connection the subscriber station is switched to data traffic.
The data traffic is thus limited to subscribers of telephone installations and to data processing devices which are directly connected to these.